The best app servers you've never heard of

Software from the likes of Allaire, Oracle and the Sun-Netscape Alliance tend to get most of the attention in the application server market. But a group of lesser-known open source technologies is becoming increasingly popular for building application servers.

These offerings - with intriguing names such as Enhydra, Midgard and Zope - feature most of the same pros and cons of other open source software. They are free and tend to be more easily customisable than their commercial counterparts, but generally lack the service and support infrastructure on which commercial software users have come to rely.

Users of open-source application servers swear by the servers, which like other application servers often sit between back-end data sources and Web servers. Most of the popular open source application servers are supported by project teams and Web sites with plenty of documentation and resources for use by potential developers.

But the bottom line, says open source user Matt Fahrner of Burlington Coat Factory Warehouse, is still that "you have to be prepared to get down and dirty and go into the code if you have problems."

While it's tough to measure use of open source applications, industry observers say Zope is among the more popular open source application servers. Based on Python, an object-oriented programming language, Zope lets end users reuse chunks of code over and over - making it ideal for building constantly changing Web applications. At Indigo Networks, a Zope application server runs a program that lets employees update the company's online shopping application. The application features products from multiple merchants and needs frequent updating, according to Ted Patrick, Indigo's chief information officer. "The Zope application server assembles everything on the fly," he says.

One of the primary reasons Indigo didn't choose a commercial application server platform, such as Microsoft's Active Server Pages, was the inability of such products to consistently reuse blocks of code. "You find that if you change one thing, you have to make a lot of changes in many places," Patrick says.

Another open source application server, Enhydra, is written in Java and is used for creating Java application servers that can either directly take HTTP-based requests or serve up data through most Web servers. One of Enhydra's strengths lies in its XML compiler's ability to separate business logic and presentation of pages - if the two are combined, it is trickier for developers to make changes. At Softcom, an application services provider, Enhydra helps developers separate Java and HTML in developing Web applications for interactive Web sites.

Midgard is also gaining notice in the open source community. Written in a PHP scripting environment, Midgard is aimed at end users who need to serve up Web-based applications on the fly. Midgard servers reside between an Apache Web server and data on an Open Database Connectivity-compliant database.

While open source software lacks the toll-free support lines that users of commercial software have become accustomed to, open source proponents say there is plenty of support available and more is emerging. In fact, users of open source application servers might find they get software problems fixed faster than they would if they were dealing with vendors, says Scott Shaw, president of Antarctica IT, a Framingham, Massachusetts firm that specializes in supporting open source code. That's because the virtual community of open source software engineers is unhampered by the rigid schedules that result in long-awaited service packs for traditional applications and operating systems, he says.

Companies such as Antarctica are also filling the void for open source support. Digital Creations, a company formed by the creators of Zope, helps customers install the free application server and build applications on it.

Still, Digital Creations CEO Paul Everitt says he "lives and breathes" the uncertainty that surrounds open source code every day trying to sell services into corporate accounts. But with validation for open source growing in the form of public companies such as Red Hat, Everitt says the job is getting easier.

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